So-called boat leveling devices of the trim-tab type have been known for many years and various forms of them have been developed in an effort to increase attitude control and stability of water crafts, as well as improving general hydrodynamic efficiency inclusive of decrease of flow velocity under the hull and fuel efficiency.
The prior art trim-tabs which typically are provided in pairs to enhance stability of the craft, are shown in FIGS. 1, 2, 3, 4, and 5 herewith. More particularly, FIG. 1 shows a traditional external trim-tab 2.1 of which is attached directly to transom 3.1 of a craft 100.1 and in which the attitude of the trim-tab is controlled through a hydraulic piston assembly 4.1 which controls relative angulation of the hull relative to level of the water. Also shown in FIG. 1 is a servo-loop wiring 9.1 by which assembly 4.1 are controlled.
The prior art shown in FIG. 2 differs from that of FIG. 1 only in that the trim tab 2.2 is positioned beneath stern 6.2 of the craft 100.2 and forward of propeller 8.2. Therein, the direction of assembly 4.2 and hydraulic piston 5.2 are aligned with the gravity vector as opposed to the angled position of the hydraulic assembly shown in the prior art of FIG. 1.
The prior art shown in FIG. 3 demonstrates the hinge common in most trim tabs, that is, a pivot hinge 1.3 that fastens the planar surface 2.3 of the trim tab to the watercraft. The pivot hinge is fixed in a specific location, and requires an actuator 5.3, mounted at a non-right angle to allow the planar surface to descend.
The prior art shown in FIG. 4 shows a similar issue where the planar surface 2.4 is fastened directly to the hull of the watercraft by a living hinge 7.4. This living hinge 7.4 is in a fixed location as well, and thus requires an actuator 5.4 mounted at a non-right angle, or the actuator 5.4 with a pivot mount to allow the planar surface 2.4 of the trim tab to descend.
The prior art shown in FIG. 5 shows an issue where the planar surface 2.5 is fastened directly to the transom of the watercraft by a bracket-like hinge 1.5. This bracket-like hinge 1.5 is in a fixed location as well, and thus requires an actuator 5.5 mounted at a non-right angle to allow the planar surface 2.5 of the trim tab to descend.
In general trim-tabs of the prior art, whether double or single acting, will operate upon the same principles and have a common objective, namely, that of contributing to the efficiency control of the boat's attitude, stabilization and general hydrodynamics.
There are significant differences between the prior art and the current invention. Primarily, the mounting of an actuator to a trim tab is direct in FIGS. 1, 2, 3, 4 and 5; meaning, looking to FIG. 4, the planar surface 2.4 is attached to driving end 8.4 of the actuator 5.4. This type of mounting is standard across all prior art trim-tabs referenced above, limiting the length of descent of the trim tabs to the actual “stroke range” of the actuator arm. “Stroke range” is a measurement dependent upon the length of the ram of the actuator. Generally, the longer the ram of the actuator the greater the angle of deflection between the hull and the trim-tab. This increase in the deflection angle increases the lift generated in the stern end of the watercraft, therefore causing the bow to lower and allow for more hydrodynamically efficient behavior from the marine craft.
Along with the increase in the angle of deflection, the forces of the water in contact with the hull and, more importantly, the trim-tab are also increased; making the stresses on the rams of the actuator bear a greater force. The current invention also allows for a distribution of the force to handle the force increase.